Fig. 2. Effects of conditioned water (CW) on larval development of Helisoma (A,C,D) and Lymnaea (B,E,F). (A,B) Incubation in CW induced developmental retardation in both Helisoma and Lymnaea. The effect disappeared after washout (CW-wash; the beginning of washout is indicated by arrows). Water conditioned by juveniles raised with plentiful food (CW-f) was ineffective. At the time when control animals developed into postmetamorphic adult like forms (C,E), the animals in CW were still at the veliger stage (D,F). Scale bars: 100 µm.